The same here, been sent about 10 letters now for entering a no driving zone after 5pm. Annoyingly got notification of the violation 2 years after the evnt and was moving accomadation at the time of the incident so had no choice but to drive into the area.

Also was working with the local police at the time so had permission but being two years later hadn't kept any records.

Apparently CLI say this is my final notice (nearly £400).

I've replied to nothing as yet.